Rhubarb is one of traditional Chinese medicinal materials in China, and a general term for various perennial plants from Rheum, Polygonaceae. Rhubarb is available for pharmaceutical use with rhizomes and roots thereof, and has a bitter-cold property and taste and invigorates spleen, stomach, large intestine, liver and pericardium meridian. Rhubarb exhibits an efficacy in cooling blood and stopping bleeding, draining fire and resolving toxin, promoting blood circulation and removing blood stasis, removing dampness through diuresis and removing jaundice, relieving constipation by purgation and so on. There are about 60 species of plants from Rheum, which are distributed in high and cold mountain areas in Asian temperate and subtropical zones. In China, there are 39 species and two varieties, which are mainly distributed in northwest, southwest and north China regions with less in northeast. In Tibetan medicines, rhubarb is classified into three grades depending on the purgation effect thereof: top, middle and low. The top grade is termed as rhubarb, the middle grade is termed as ya-rhubarb, and the low grade is termed as small-rhubarb. It has been found through research in recent years that stilbenoid compounds are characteristic components in Sect. Rheum plants from Rheum. 
Stilbenoid compounds, also referred to as diphenylethylene compounds, are active ingredients extensively present in Rheum, Polygonaceae. It has been found through research that, stilbenoid compounds play a role in anti-aging, preventing and treating senile dementia, improving learning and memory, brain protection and neuroprotection, regulating blood lipids, anti-atherosclerosis, anti-thrombus, antioxidation for scavenging free radicals, protecting the nervous system, anti-tumor, lowering cholesterol, liver protection, vasodilatation and protection, skin protection, anti-depression, heart and myocardial protection, effects on diabetes, promoting hair growth, strengthening bones and so on. Among the above, activities such as anti-thrombus, skin protection, anti-depression, heart and myocardial protection, effects on diabetes, promoting hair growth, strengthening bones and so on are newly reported in recent years. Therefore, it is of very good social and economic benefits to develop and use stilbenoid compounds in rhubarb. As a result, it has been critical for the development of rhubarb to find a rapid, convenient and inexpensive method for extracting stilbenoid compounds from rhubarb.
Flash extraction is a new extraction method developed in recent years. Flash extraction is based on the principle of tissue disruption extraction, where materials are rapidly disrupted into an appropriate particle size in a flash extractor with a suitable solvent, meanwhile, high-speed stirring, super vibration, diafiltration under reduced pressure and other functions are further present in flash extraction so as to achieve the purpose of extraction. Since one extraction generally can be completed in several seconds to several minutes in flash extraction, the extraction speed thereof is more than one hundred-times of a traditional method. However, the flash extraction method employed in the prior art can only improve the extraction speed, while makes little effects on the content of active ingredients.